Ballistic resistant articles such as bulletproof vests, curtains, mats, raincoats and umbrellas containing high strength fibers are known. Fibers conventionally used include aramid fibers such as poly(phenylenediamine terephthalamide), nylon fibers, glass fibers and the like. For many applications, such as vests or parts of vests, the fibers are used in a woven or knitted fabric.
In "The Application of High Modulus Fibers to Ballistic Protection", R. C. Laible, et al., J. Macromol. Sci.-Chem. A7(1), pp. 295-322 1973, it is indicated on p. 298 that an important requirement is that the textile material have a high degree of heat resistance; for example, a polyamide material with a melting point of 255.degree. C. appears to possess better impact properties ballistically than does a polyolefin fiber with equivalent tensile properties but a lower melting point.
R. C. Laible; "Fibrous armor," Ballistic Materials and Penetration Mechanics, Elsevier Scientific Publishing Co., 1980; provides an overview of the ballistic resistance performance of various fabrics. Liable discloses that among different silk fabrics, a fabric having a lower areal density would exhibit a small increase in ballistic resistance to .22 caliber fragments. See in particular, pp. 73-90 thereof. J. W. S. Hearle, et al.; "Ballistic Impact Resistance of Multi-Layer Textile Fabrics," NTIS Acquisition No. AD A127641, (1981); disclose that among nylon fabrics, those having greater areal density exhibited increased ballistic resistance. The findings of R. Sarson, et al.; 11th Commonwealth Defense Conference on Operational Clothing and Combat Equipment, India (1975); were in agreement with the findings of Hearle, et al. Weiner, et al.; "Materials Evaluation Report No. 2781," U.S. Army Natick R&D Command Ma. (1950); found no significant effect of fabric areal density on ballistic resistance. Figucia; "Energy Absorption of Kevlar Fabrics under Ballistic Impact" NTIS Acquisition No. AD A090390, (1980); discloses a limited study employing Kevlar fabric in which ballistic resistance increased with a decrease in fabric areal density. However, these results are not readily interpreted because the type of fabric weave was not held constant.
It is, therefore, apparent that there is no generally applicable relationship between fabric areal density and ballistic resistance.